Oxide skin treatment method for high-nickel stainless steel hot-rolled coil

Abstract

The invention discloses an oxide skin treatment method for a high-nickel stainless steel hot-rolled coil. The technical problem that the oxide skin treatment efficiency of the high-nickel stainless steel hot-rolled coil is low is solved. The oxide skin treatment method comprises the following steps: S1, carrying out heating annealing treatment on a steel strip; s2, salt bath dephosphorization treatment is conducted on the steel strip through a salt bath device; s3, water-cooling phosphorus explosion treatment is conducted on the steel belt through a rinsing device; s4, the steel strip is subjected to acid pickling treatment through an acid pickling section; in the step S2, a molten salt bath medium composed of NaOH, NaNO3 and NaCl is contained in the salt bath device, and the molten salt bath medium and oxide skin on the surface of the steel strip are subjected to a chemical reaction, so that chemical phosphorus removal is achieved; and in the step S3, rinsing liquid is contained in the rinsing device and used for washing oxide skin on the surface of the steel strip, so that the oxide skin falls off. According to the method, the oxide skin can be quickly and effectively treated, the treatment efficiency of the oxide skin is improved, the production cost is reduced, and the product quality is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of stainless steel production and processing, and particularly relates to a scale treatment method for high-nickel stainless steel hot-rolled coils. BACKGROUND

[0002] High-nickel stainless steel has excellent corrosion resistance, superior mechanical properties, good thermal stability, good processing performance, high strength, and light weight, and the like, and part of the thick specifications and wide width high-nickel stainless steel hot-rolled coils can replace stainless steel medium plates in multiple fields, and are widely used in chemical industry, energy field, environmental protection engineering, high-end manufacturing industry, marine engineering, emerging technology field, and the like, and are one of the key basic materials indispensable in various industrial fields, and the quality level has the most direct influence on the safety and stability of chemical production.

[0003] At present, the high-nickel stainless steel hot-rolled coil is produced through a hot-rolled annealing pickling line, sequentially heated through a coal gas or natural gas horizontal heating furnace, pellet blasted through a shot blasting machine, bent through a phosphorus breaking machine, and pickled and passivated through an acid pickling section, so as to realize the scale treatment of the high-nickel stainless steel hot-rolled coil.

[0004] The scale treatment process of the high-nickel stainless steel hot-rolled coil in the related art has the following problems:

[0005] (1) The scale of the high-nickel steel is dense, and the chemical structure of the scale has strong corrosion resistance, so that the production efficiency is low and the production cost is high during the hot-rolled annealing pickling line production;

[0006] (2) The scale is difficult to be pickled, and easily causes defects such as iron phosphorus pitting, thereby affecting the quality of the product. SUMMARY

[0007] In order to solve all or part of the above problems, the purpose of the present application is to provide a scale treatment method for high-nickel stainless steel hot-rolled coils, which can realize rapid and effective efficiency of the scale, improve the treatment efficiency of the scale, reduce the production cost, and improve the quality of the product.

[0008] The present application provides a scale treatment method for high-nickel stainless steel hot-rolled coils, comprising the following steps:

[0009] S1, heating and annealing treatment is performed on the steel strip;

[0010] S2, salt bath phosphorus removal treatment is performed on the steel strip through a salt bath device;

[0011] S3, water cooling phosphorus explosion treatment is performed on the steel strip through a rinsing device;

[0012] S4, acid pickling treatment is performed on the steel strip through an acid pickling section;

[0013] In S2, the salt bath device contains molten salt bath medium composed of NaOH, NaNO3 and NaCl, and is used to react with the oxide skin on the surface of the steel strip to achieve chemical descaling;

[0014] In S3, the rinsing device contains rinsing liquid, and is used to flush the oxide skin on the surface of the steel strip to make the oxide skin fall off.

[0015] Optionally, in S1:

[0016] The steel strip is heated by a horizontal heating furnace.

[0017] Optionally, in S2:

[0018] The weight ratio of the components of the molten salt bath medium is controlled to be NaOH:NaNO3:NaCl=6:3:1, and the temperature of the molten salt bath medium is controlled to be 450-550℃.

[0019] Optionally, in S2:

[0020] If the content of NaCl in the molten salt bath medium exceeds 15% of the total components, 1-2% of Na2CO3 buffer of the total components is added to the molten salt bath medium.

[0021] Optionally, in S3:

[0022] The temperature of the rinsing liquid is controlled to be 80±5℃.

[0023] Optionally, the salt bath device comprises:

[0024] A salt bath pool for containing the molten salt bath medium;

[0025] A heating assembly arranged on the salt bath pool and used to heat the molten salt bath medium;

[0026] Two guide compression rollers horizontally rotating in the salt bath pool, respectively, the bottoms of the two guide compression rollers are immersed in the molten salt bath medium, and the steel strip passes below the two guide compression rollers;

[0027] Two tension rollers horizontally rotating in the salt bath pool, respectively, the two tension rollers are located above the liquid level of the molten salt bath medium, and the steel strip passes between the two tension rollers.

[0028] Optionally, the two guide compression rollers are made of steel.

[0029] Optionally, two slip wiping motors are arranged on the salt bath pool, the output shafts of the two slip wiping motors are coaxially connected with the corresponding guide compression rollers, respectively, and the slip wiping motors are used to control the corresponding guide compression rollers to rotate synchronously with the steel strip.

[0030] Optionally, the heating assembly comprises a plurality of heating rods, and the plurality of heating rods are respectively detachably arranged on the salt bath pool.

[0031] Optionally, the rinsing device comprises:

[0032] a rinsing pool for containing rinsing liquid;

[0033] a guide rubber roller horizontally rotatably connected in the rinsing pool, a bottom of the guide rubber roller being immersed in the rinsing liquid, and the steel belt passing below the guide rubber roller.

[0034] From the above technical solution, the oxide skin treatment method for the high-nickel stainless steel hot-rolled coil provided by the present application has the following advantages:

[0035] The oxide skin treatment method can realize rapid and effective treatment of the oxide skin on the surface of the high-nickel stainless steel hot-rolled coil, improve the treatment efficiency of the oxide skin, reduce the production cost, and improve the product quality.

[0036] Other features and advantages of the present application will be described in the subsequent description. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0038] Figure 1 is a process flow chart of the oxide skin treatment method in the embodiments of the present application;

[0039] Figure 2 is a structural schematic diagram of the salt bath device and the rinsing device in the embodiments of the present application;

[0040] Figure 3 is a structural schematic diagram of the salt bath device in the embodiments of the present application;

[0041] Figure 4 is a structural schematic diagram of the rinsing device in the embodiments of the present application.

[0042] Explanation of reference signs:

[0043] 1, salt bath device; 11, salt bath pool; 12, heating assembly; 121, heating rod; 13, guide compression roller; 14, tension roller; 2, rinsing device; 21, rinsing pool; 22, guide rubber roller. DETAILED DESCRIPTION

[0044] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application will be described in detail below with reference to the drawings. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other in any manner without conflict.

[0045] As Figure 1 , Figure 2 , Figure 3 , Figure 4 The present application discloses a scale treatment method for high-nickel stainless steel hot-rolled coil, which comprises the following steps:

[0046] S1, heating annealing treatment is performed on the steel strip;

[0047] S2, salt bath dephosphorization treatment is performed on the steel strip by a salt bath device 1;

[0048] S3, water cooling dephosphorization treatment is performed on the steel strip by a rinsing device 2;

[0049] S4, pickling treatment is performed on the steel strip by a pickling section;

[0050] In S1, the steel strip is heated by a horizontal heating furnace, and in other embodiments, other heating devices can also be used to heat the steel strip.

[0051] In S2, the salt bath device 1 contains a molten salt bath medium composed of NaOH, NaNO3 and NaCl, which can chemically react with the scale on the surface of the steel strip to achieve chemical dephosphorization. Meanwhile, the weight ratio of the components of the molten salt bath medium is controlled to be NaOH: NaNO3: NaCl = 6:3:1, and the temperature of the molten salt bath medium is controlled to be 450-550℃.

[0052] The scale on the surface of the stainless steel is composed of:

[0053] Outer layer: Fe2O3 / Fe3O4(loose layer);

[0054] Middle layer: Cr2O3(dense layer);

[0055] Inner layer: FeO·Cr2O3spinel structure.

[0056] Therefore, the scale structure is destroyed by the chemical penetration of the molten salt bath medium, the alkaline environment (NaOH) can dissolve SiO2 and other insoluble oxides, and the oxidizing agent (NaNO3) can convert low-valence chromium oxides into soluble chromate, thereby achieving the effect of removing the scale. The specific mechanism is that the components act as follows:

[0057] Utilizing NaOH to maintain alkaline environment, utilizing NaNO3 to provide continuous oxidation ability, together to promote the formation of Fe3O4 / Cr2O3-based composite oxide film.

[0058] (1) The role of NaOH:

[0059] Providing strong alkaline environment (pH> 13);

[0060] Promoting the formation of Cr2O3 passivation film;

[0061] Dissolving surface silicates and other impurities.

[0062] Typical reaction as follows:

[0063] Fe3O4+4NaOH→2NaFeO2+Na2FeO2+2H2O

[0064] 2Cr+6NaOH+3[O]→2Na3CrO4+3H2O

[0065] NiO+2NaOH→Na2NiO2+H2O↑

[0066] (2) The role of NaNO3 (sodium nitrate):

[0067] High temperature oxidant (decomposition above 450℃)

[0068] Providing active oxygen atoms [O];

[0069] Inhibiting the excessive conversion of Fe 2+ to Fe 3+ .

[0070] Typical reaction as follows:

[0071] 2NaNO3→2NaNO2+O2↑

[0072] 2Cr2O3+3NaNO3→2Na2CrO4+NO↑

[0073] NiO+NaNO3→NaNiO2

[0074] Fe2O3+NaNO3→NaFeO2+NO2↑

[0075] (3) The role of NaCl:

[0076] Adjusting the flowability of molten salt;

[0077] Enhancing ion conduction as electrolyte;

[0078] Promoting the uniformity of oxide film in cooperation with NaOH.

[0079] In the embodiment, the temperature of the molten salt bath medium is preferably 530±10℃, and the salt bath time is set according to the annealing efficiency to avoid the problem of intergranular corrosion caused by the long residence time of the steel strip in the molten salt bath medium.

[0080] In S2, if the content of NaCl in the molten salt bath medium exceeds 15% of the total components, the destruction of the passivation film by chloride ions will be accelerated, and the tendency of intergranular corrosion will be induced. Therefore, 1-2% of Na2CO3 buffer is added to the molten salt bath medium to reduce the proportion of NaCl to below 5%.

[0081] In S3, the rinsing device 2 contains rinsing liquid and is used to flush the oxide scale on the surface of the steel strip to make the oxide scale fall off. At the same time, the temperature of the rinsing liquid is controlled to be 80±5℃.

[0082] After the salt bath treatment, a large amount of oxide scale falls off, and the originally dense oxide scale becomes loose. When the steel strip enters the rinsing device from the salt bath device, the temperature of the steel strip is about 500℃. The rinsing device can reduce the temperature of the steel strip and achieve water explosion phosphorization under the action of quenching to make the oxide scale fall off. At the same time, the rinsing device can also flush away the alkali solution to reduce the consumption of acid solution in the subsequent process. Water explosion phosphorization refers to the fact that under the action of quenching, the oxide scale on the surface of the steel strip can become loose and cracked, and when passing through the rinsing liquid, the rinsing liquid can flush the oxide scale to make it fall off.

[0083] In one embodiment, as shown in Figure 2 , Figure 3 The salt bath device 1 comprises a salt bath pool 11 for containing the molten salt bath medium. The salt bath pool 11 is provided with a heating assembly 12 for heating the molten salt bath medium. Two guide compression rollers 13 are horizontally connected in the salt bath pool 11, the bottoms of the two guide compression rollers 13 are respectively immersed in the molten salt bath medium, and the steel strip passes below the two guide compression rollers 13. Two tension rollers 14 are horizontally connected in the salt bath pool 11, the two tension rollers 14 are respectively located above the liquid level of the molten salt bath medium, and the steel strip passes between the two tension rollers 14.

[0084] In one embodiment, as shown in Figure 2 , Figure 3 Since the temperature of the molten salt bath medium is about 500℃, ordinary rubber rollers cannot be used as the guide and support of the steel strip. Therefore, the two guide compression rollers 13 are respectively made of steel to withstand high temperature and ensure the guidance and support of the steel strip.

[0085] In one embodiment, as shown in Figure 2 , Figure 3As shown, the salt bath tank 11 is provided with two friction motors (not shown in the figure), the output shafts of the two friction motors are coaxially connected with the corresponding guide compression rollers 13 respectively, and the friction motors are used to control the corresponding guide compression rollers 13 to rotate synchronously with the steel belt. In the embodiment, the guide compression rollers 13 keep consistent with the speed of the steel belt, that is, the problem of relative sliding between the guide compression rollers 13 and the steel belt is prevented, thereby reducing the risk of scratching the surface of the steel belt and ensuring the quality of the product.

[0086] In one embodiment, as shown in Figure 2 、 Figure 3 The heating assembly 12 includes a plurality of heating rods 121, which are detachably arranged on the salt bath tank 11, so that the heating rods 121 can be replaced, thereby reducing the maintenance cost. In the embodiment, the plurality of heating rods 121 are arranged at equal intervals to improve the heating uniformity and ensure the constant temperature of the molten salt medium in the salt bath tank 11.

[0087] In one embodiment, as shown in Figure 2 、 Figure 4 The rinsing device 2 includes a rinsing tank 21 for containing rinsing liquid, and a guide rubber roller 22 is horizontally rotatably connected in the rinsing tank 21, the bottom of the guide rubber roller 22 is immersed in the rinsing liquid, and the steel belt passes below the guide rubber roller 22.

[0088] As described above, the scale treatment method is used to remove phosphorus from the high-nickel stainless steel hot-rolled coil by salt bath, instead of shot blasting machine and phosphorus breaking machine, the process is simpler, the phosphorus removal effect is better, the efficiency is higher, and the production cost is lower. At the same time, the mechanical phosphorus removal of the shot blasting machine is more delicate on the surface of the stainless steel, which effectively improves the quality of the product.

[0089] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should be understood as the usual meanings understood by the skilled person in the field to which the present application belongs.

[0090] In addition, the terms "first", "second", and the like are only for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0091] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for treating the oxide scale on hot-rolled coils of high-nickel stainless steel, characterized in that, Includes the following steps: S1, heat annealing treatment of steel strip; S2, the steel strip is subjected to salt bath dephosphorization treatment by salt bath device (1); S3, the steel strip is subjected to water-cooled phosphorus treatment by rinsing device (2); S4, the steel strip is pickled in the pickling section; In S2, the salt bath device (1) contains a molten salt bath medium composed of NaOH, NaNO3 and NaCl, which is used to chemically react with the oxide scale on the surface of the steel strip to achieve chemical dephosphorization. In S3, the rinsing device (2) contains rinsing liquid and is used to rinse the oxide scale on the surface of the steel strip so that the oxide scale is removed.

2. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 1, characterized in that, In S1: The steel strip is heated in a horizontal heating furnace.

3. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 1, characterized in that, In S2: The weight ratio of each component in the molten salt bath medium is controlled to be NaOH:NaNO3:NaCl = 6:3:1, and the temperature of the molten salt bath medium is controlled to be 450-550℃.

4. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 1, characterized in that, In S2: If the NaCl content in the molten salt bath medium exceeds 15% of the total components, add 1-2% of the total components of Na2CO3 buffer to the molten salt bath medium.

5. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 1, characterized in that, In S3: The temperature of the rinsing solution should be controlled at 80±5℃.

6. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 1, characterized in that, The salt bath device (1) includes: Salt bath pool (11) is used to hold molten salt bath medium; A heating assembly (12) is disposed on the salt bath (11) and is used to heat the molten salt bath medium; Two guide rollers (13) are horizontally rotatably disposed in the salt bath (11). The bottoms of the two guide rollers (13) are respectively immersed in the molten salt bath medium, and the steel strip passes under the two guide rollers (13). There are two tension rollers (14), which are horizontally rotatably arranged in the salt bath (11). The two tension rollers (14) are located above the surface of the molten salt bath medium, and the steel strip passes between the two tension rollers (14).

7. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 6, characterized in that, The two guide rollers (13) are made of steel.

8. The method for treating oxide scale on hot-rolled high-nickel stainless steel coils according to claim 6, characterized in that, Two rubbing motors are provided on the salt bath (11). The output shafts of the two rubbing motors are coaxially connected to the corresponding guide rollers (13), and the rubbing motors are used to control the corresponding guide rollers (13) to rotate synchronously with the steel belt.

9. The method for treating oxide scale on high-nickel stainless steel hot-rolled coils according to claim 6, characterized in that, The heating assembly (12) includes a plurality of heating rods (121), which are detachably mounted on the salt bath (11).

10. The method for treating oxide scale on hot-rolled high-nickel stainless steel coils according to claim 1, characterized in that, The rinsing device (2) includes: Rinse tank (21) is used to hold rinsing solution; The guide roller (22) is horizontally rotatably connected to the rinsing tank (21), with the bottom of the guide roller (22) immersed in the rinsing liquid, and the steel belt passing under the guide roller (22).

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